1. Field of the Invention
The present invention relates to an image projection apparatus, and more particularly, to an image projection apparatus for forming red (R), green (G), and blue (B) color bars on a single panel using light switches arranged in the structure of square matrix. This Application claims priority from Korean Patent Application No. 2002-0018095, filed Apr. 2, 2002, which is incorporated in full herein by reference.
2. Description of the Prior Art
A projector or a projection system displays an image by projecting an inputted image signal onto a screen. Such a display device is used to aid in a presentation at a meeting, or used in places such as a theater or home.
A conventional method used in order to realize a wide vision in the display device is magnifying an image displayed on a Liquid Crystal Display (LCD), a Cathode Ray Tube (CRT) or some such other display with a lens and projecting the image onto a screen. However the conventional method may be advantageous in achieving the wide vision, yet it is relatively weak in guaranteeing a clear image quality. In order to solve this problem, an image projection apparatus employing a Digital Micromirror Device (DMD) panel has been suggested.
The DMD is a semiconductor light switch using a micro drive mirror, i.e. micromirror. This micromirror controls a deflection of light according to an inputted image signal. In the DMD according to a digital method, a reproduction of color of the image signal is excellent and also a contrast between light and shade is clear. Since the DMD does not require A/Dxc2x7D/A conversion, a clear image can be obtained. Also, since there is no loss of light that is caused by a polarizing filter, the DMD can obtain large amount of light output.
FIG. 1 is a view showing a basic structure of a conventional image projection apparatus using a color wheel.
Referring to FIG. 1, the conventional image projection apparatus 100 using a conventional color wheel comprises a light source 110, a color wheel 120, a DMD panel 130, and a projection lens 140. A light path of white light is indicated by one-dotted line in FIG. 1.
The light source 110 emits the white light using an arc lamp or a laser beam. The color wheel 120 is rotated by a rotation driver in an arrowed direction of FIG. 1 and has R (red), G (green), and B (blue) regions.
The white light emitted from the light source 110 is subdivided into R.G.B. beams by the R.G.B. regions.
The DMD panel 130 comprises a plurality of micromirrors 130a. The R.G.B. beams divided according to the respective wavelengths are projected onto the DMD panel 130 and then deflected from the micromirrors 130a. The deflected R.G.B. beams penetrate the projection lens 140 and are formed on the screen as an image.
The conventional image projection apparatus 100 can process response signals with respect to the divided R.G.B. beams rapidly due to the presence of the individually operated micromirror 130a. That is, with a simplified structure, excellent quality of color image can be realized.
However, when a color filter such as the color wheel 120, and the DMD panel 130 are used to form an image, the DMD panel 130 uses only ⅓ amount of the white light emitted from the light source 110. For example, with respect to the R region of the color wheel 120, the R beam penetrates the color wheel 120, while the G and B beams are blocked by the color wheel 120 and discarded. This phenomenon occurs with respect to the G and B beams.
Accordingly, since only ⅓ amount of the incident white light is used in the color filtering method, a brightness of the image is reduced to ⅓. That is, since the amount of white light emitted from the light source 100 is reduced while penetrating the color wheel 120, light efficiency deteriorates and optimal brightness of the image cannot be obtained.
An object of the present invention is to provide an image projection apparatus capable of enhancing the use of light that is decreased to ⅓ at a single panel, by using a high reflective mirror.
The above object of the present invention is achieved by providing an image projection apparatus comprising: a light source for emitting a plurality of monochromatic color beams having different wave lengths; a first light transmit unit having a plurality of optical fibers which the respective monochromatic color beams pass through; a light switch unit having a plurality of mirrors for selectively deflecting the monochromatic color beams at a predetermined angle; a quadrangular beam generating unit for converting the reflected monochromatic color beams into quadrangular beams having certain ratios of length to height; a single panel for receiving the converted quadrangular beams and forming a monochromatic color bar on at least one portion of upper, mid, and lower portions thereof; and a projection lens unit disposed opposite to the single panel.
More specifically, the light switch unit comprises a plurality of output ports disposed at output terminals thereof, for outputting the monochromatic color beams. The monochromatic color beam deflected from a first mirror among the plurality of mirrors is output through an output port corresponding to the first mirror. The image projection apparatus further comprises a second light transmit unit having a plurality of optical fibers for transmitting the monochromatic color beam output from the output port into the quadrangle beam generating unit.
The mirror comprises: a deflection mirror having one deflection surface; and a drive unit for driving the deflection mirror such that the defection mirror varies from a first position to a second position, the reflection mirror at the first position deflects the monochromatic color beams to any one of the upper, mid, and lower portions of the panel, the reflection mirror at the second position allows the monochromatic color beams to pass therethrough.
The light switch unit has the mirrors arranged according to a square matrix structure of (nxc3x97n), with n being a positive number greater than or equal to 3. The light switch unit is operated such that only one mirror is positioned at the first position with respect to one row and one column. The mirrors are Micro Electro Mechanical System (MEMS) mirrors.
Each of the (nxc3x97n) mirrors is positioned at the first position at least one time by a predetermined order to realize one image. The n equals the number of monochromatic color beams of different wavelengths emitted from the light source. A predetermined order comprises an illumination sequence of n light illuminations.
And during one sequence, each of the upper, mid, and lower portions of the panel receives at least one illumination from each of the monochromatic color beams of different wavelengths emitted from the light source.
The panel is a Digital Micromirror Device (DMD) for modulating the plurality of the monochromatic color bars into a digital signal and deflecting the signal to the projection lens unit. The projection lens unit concentrates the incident beams from the panel and projects the beam onto a display device.
The above object of the present invention is achieved by providing an image projection apparatus comprising: light source means for emitting a plurality of monochromatic color beams having different wave lengths; light switch means having a plurality of mirrors for selectively deflecting the monochromatic color beams at a predetermined angle; quadrangular beam generating means for converting the reflected monochromatic color beams into quadrangular beams having certain ratios of width to height; and panel means for receiving the converted quadrangular beams by formation of a monochromatic color bar on at least one of an upper, mid, and lower portion thereof.
More specifically, the light switch means has the plurality of mirrors arranged according to a square matrix structure of (nxc3x97n), with n being a positive integer greater than or equal to 3
According to the present invention, the R.G.B color bars are formed by using light switches arranged in the structure of square matrix of 3xc3x973, thereby improving the utilization efficiency of the light.